1. Field of the Invention
The invention generally relates to intraluminal devices and, more particularly, devices used to monitor intraluminal characteristics.
2. Brief Description of Related Technology
In recent years, stents have come to play an essential role in the treatment of cardiovascular diseases. A stent typically has mesh-like walls in a tubular shape, and once positioned by a catheter, is expanded radially by the inflation of an angioplasty balloon. Stents are implanted by such procedures to physically expand and scaffold coronary and other arteries that have been narrowed by plaque. However, re-closures often occur due to recoil of the blood vessels, further plaque deposition, or spasms.
Monitoring of blood flow can provide advance notice of such failures and, thus, continuing measurement of blood flow is therefore important for long-term monitoring of vascular diseases. Implantable pressure sensors are promising devices for continuous monitoring of blood pressure and flow rate, and could provide advance notice of restenosis, which is a common failure mechanism for stents. Detection mechanisms proposed in the past for implantable sensors include thermal resistor, blood conductivity, and differential pressure measurement using capacitive diaphragms.
Wireless monitoring of cardiac parameters has been used to ease the delivery of information from implanted measurement devices. Passive telemetric sensing of pressure has been implemented using an implanted microchip with a planar thin film inductor fabricated together with a micromachined capacitive pressure sensor. See, for example, E. Park, et al., “Hermetically Sealed Inductor-Capacitor (LC) Resonator for Remote Pressure Monitoring,” Jpn. J. Appl. Phys., Vol. 37, pp. 7124-28 (1998). This L-C tank circuit couples to a separate, external transmitting coil via mutual inductance. The change in pressure can be detected by the shift in frequency at which the external coil shows a characteristic dip in impedance and phase.
Despite these advances in implantable devices and wireless monitoring methods, the implementation and deployment of such devices is complicated by the presence of the thin-film inductor necessary for passive telemetry. The prior art also does not sufficiently teach or suggest to one of ordinary skill in the art how to utilize stents, of either existing or novel design, in the implementation, deployment and operation of such implantable measurement devices. Still further, the prior art does not sufficiently teach or suggest to one of ordinary skill in the art a stent device capable of maintaining the patency of a lumen while also monitoring one or more intraluminal characteristics.